Bulk Polymerization of PEGDA in Spruce Wood Using a DBD Plasma-Initiated Process to Improve the Flexural Strength of the Wood–Polymer Composite

Abstract

The chemical treatment of wood has been shown to increase its mechanical strength by forming composites with a variety of polymers. Polyethylene glycol diacrylate (PEGDA) has commonly been used as a polymer reinforcement to increase the strength and resistance of spruce wood for various applications, such as protection from weathering. In this study, PEGDA was impregnated into wood samples and polymerized by dielectric barrier discharge (DBD) plasma to form wood–polymer composites (WPCs). The kinetic rate order of PEGDA was explored using FT-IR quantitative analysis and the DBD plasma-initiated polymerization was determined to be second order. The strength of the wood samples was then determined by a three-point flexural test. The PEGDA-treated spruce wood samples showed improved flexural strength versus the untreated wood samples. The WPCs were also made using a UV treatment method and were then compared to the DBD plasma-treated samples. The results showed that the DBD plasma-treated samples yielded superior flexural strength relative to the UV-treated samples. We accredited this difference in strength to the plasma process and its ability to penetrate into the various layers of the wood and initiate polymerization, as opposed to UV light that can only penetrate superficially, initiating polymerization in only the first few layers of the wood surface.

Bulk Polymerization of Acrylic Acid Using Dielectric-Barrier Discharge Plasma in a Mesoporous Material

“…As can be seen in Figure 3a, the peak area ratio (A1/A0) of these two bands were used to semi-quantitatively demonstrate the successful polymerization of AA by DBD plasma. The semi-quantitative analysis method for determining the reaction rate order using FTIR was adapted from Pintar et al [35] and was used in a previous paper to demonstrate the degree of conversion of PEGDA using DBD plasma [32]. A second-order treatment of the data yielded the best linear fit, with an R-squared value of 0.98218 (Figure 3b).…”

“…This nomenclature serves to differentiate this approach from the conventional gaseous plasma polymerization method. In comparison to other polymerization methods, non-gaseous DBD plasma polymerization is a favored method for polymerization in mesoporous materials since atmospheric-pressure plasma has been seen to penetrate planar mesoporous substrates with thicknesses similar to paper and even in thin wood planks (1-2 mm in thickness) [32]. This internal polymerization in thicker substrates is mostly due to the sample preparation, where the mesoporous substrate to be polymerized is soaked and effectively impregnated with the liquid monomer and then subsequently polymerized by plasma initiation.…”